Rangers midfielder Joey Barton is being investigated over claims he gambled on Celtic's 7-0 defeat by Barcelona.
Scottish Football Association rules prohibit players, coaches, referees and officials from betting on football anywhere in the world.
The SFA says it cannot comment on the matter, which threatens 34-year-old Barton's future at the club.
On Monday, the former England and QPR player was suspended by Rangers after a training ground disagreement last week.
SFA rules state: "No club, official, team official or other member of team staff, player, match official or other person under the jurisdiction of the Scottish FA shall gamble in any way on a football match."
Hampden chiefs and the Gambling Commission are looking into the claims following Brendan Rodgers' side's 7-0 defeat in their Champions League Group C opener at the Nou Camp.
|Gambling in Scottish football|
|Sept 2013: Rangers midfielder Ian Black became the first player in Scotland to be punished for breaking gambling rules, receiving a 10-match ban, seven of which were suspended until the end of the season. He was also fined £7,500. He was accused of gambling on 160 matches over a seven-year period while at Inverness CT, Hearts and Rangers, including betting against his own team on three occasions. He did not play in any of the matches concerned.|
|Feb 2014: Ayr United striker Michael Moffat was suspended for six games, later reduced on appeal, for placing seven bets on six matches involving his own team. He avoided a fine but was also found guilty of placing an additional 150 bets on other games. There was no evidence to suggest Moffat has been involved in match-fixing or influencing results.|
|April 2015: The SFA was unsuccessful in appealing against what they saw as the "unduly lenient" punishment given to Rangers goalkeeper Steve Simonsen for betting on games. The 35-year-old was given a two-match ban - one suspended until the end of the season - after being found guilty of betting on 55 games. Simonsen bet on 18 matches in season 2013-14 and 37 the following season. None of these fixtures involved Rangers, and the former England Under-21 international claimed he had misunderstood the SFA's rules governing players' gambling.|
|May 2015: Partick Thistle midfielder Steven Lawless was banned for six matches, four of which were suspended until the end of the following season, for betting on 513 matches between December 2012 and March 2015. Lawless was not involved in any of the matches.|
BBC Scotland senior football reporter Chris McLaughlin:
"Few would now argue against the feeling that Joey Barton's career at Rangers is over, but it appears to be ending in quite spectacular fashion.
"Less than 24 hours after he was suspended by the club after a training-ground bust-up, a front-page story suggests he broke football gambling rules by betting on a match. If the club is gathering evidence to prove the 34-year-old is in breach of contract, it certainly goes some way to helping their cause, if true.
"Just a day before the launch of his book, for the publishers, it's the perfect storm. Add into the mix a few lines from the man himself about his regrets at signing for Rangers and claims that Celtic tried to sign him first, and you have the Joey Barton circus in full swing."